Valve stem seal assembly

ABSTRACT

A valve stem seal assembly formed from a thin sheet of wear resistant filled Teflon assembled with a sheet metal retainer to provide an extended lip urged to sealing engagement with the valve stem by resilient fingers of the retainer and having means to seal against and retain the assembly on the valve guide. One embodiment is installed on the valve guide in a partially formed state and the final configuration of the lip and resilient fingers is formed after assembly to correct for eccentricity of the valve guide and the seal mounting.

United States Patent [72] Inventor Carlisle R. Davis, Jr.

Grand Blanc, Mich. [211 Appl. No. 647,674 [22 Filed Juhe 21, 1967 [45]Patented Jar 12, 1971 [73] Assignee General Motors Corporation Detroit,Mich. a corporation of Delaware [54] VALVE STEM SEAL ASSEMBLY 1 Claim, 7Drawing Figs.

[52] US Cl 277/149, 277/178, 277/205 [51] Int. Cl Fl6j 9/06 [50] FieldofSearch... 277/149, 33.188, 205,235,178,152,199;251/337; 123/ 188? [56]References Cited UNITED STATES PATENTS 3,114,561 12/1963 Creath et a].277/205X 3,300,225 1/1967 Shepler 277/188X 3,306,620 2/ 1967 Taschenberg277/188X 3,379,445 4/1968 Fisher 277/178 7 FOREIGN PATENTS 1,258,9723/1961 France 277/152 581,593 10/1946 Great Britam.... 277/152 589,7686/ 1947 Great Britain 277/ 152 Primary Examinerl.aveme D. GeigerAssistant Examiner-Jeffrey S. Mednick Attorneys-J. L. Carpenter, W. F.Wagner and Robert J.

Outland ABSTRACT: A valve stem seal assembly formed from a thin sheet ofwear resistant filled Teflon assembled with a sheet VALVE STEM SEALASSEMBLY SPECIFICATION This invention relates to valve stem seals andmore particularly to a seal assembly for use in an'intemal combustionengine to control the leakage of lubricating oil from the rockercompartment through the valve guides and into the engine combustionchamber.

In modern overhead valve internal combustion engines of the automotivetype, it is known to utilize seals between the valve guides and thevalve stems which extend therethrough in order to control the leakage oflubricating oil through the valve guides. This is particularly importantin the case of the intake valves since the reduced pressure of theintake passages tends to draw substantial amounts of oil through theclearance between the valve and the valve guide if adequate means arenot utilized to prevent it. Such seals are, however, also used on engineexhaust valves.

To perform its function, a valve stem seal must provide adequately formisalignment between the valve stem and the mounting location of theseal on the valve guide. Further, it must have a long-wear life to matchthe extended periods between overhauls which are common in todaysengines. In addition, the fact that a seal is used on each valve of anengine makes it particularly desirable that the seal be economical bothin its original cost and the expense of installation.

The present invention provides a valve stem seal assembly whichadequately meets the foregoing requirements by providing a constructioncomprising a sheet metal retainer assembled with a thin sheet ofwear-resistant filled Teflon seal material. The seal material has anextending frustoconical lip which is held in engagement with the valvestem by resilientfingers of the sheet metal retainer and is sufficientlylong to provide for reasonable eccentricity between the valve stem andthe seal mounting. Varying alternate embodiments of the seal asemblyprovide for mounting either in a counterbore at the end of the valveguide or on the outer diameter of the valve guide itself. In botharrangements, radial flange portions of the seal assembly provide forsealing on a surface of the valve guide. One embodiment of the design isarranged to have the seal lip formed in place after installation on thevalve guide so that concentricity of the seal with the valve stem isassured.

These and other features of the present invention will be more clearlyseen from the following description of selected embodiments chosen forpurposes of illustration, referring to the drawings, in which:

FIG. 1 is a fragmentary cross-sectional view of an internal combustionengine utilizing a valve stem seal assembly according to the invention;

FIG. 2 is an enlarged cross-sectional view showing the seal installationof FIG. I;

FIG. 3 is an enlarged cross-sectional view of a seal installationsimilar to FIG. 2 but in which the seal assembly includes modifiedretention means;

. FIG. 4 is a cross-sectional view ofthe construction of FIG. 3 taken inthe plane indicated by the line 4-4of the FIG.;

FIG. 5 is a pictorial view of an alternative embodiment of a sealassembly according to the invention shown in a'- partial state ofcompletion and partially broken away to show certain details of-theconstruction; 7

FIG. 6 is a cross-sectional viewshowing the seal of FIG. 5 in completedstate as installed in an engine; and

' FIG. 7 is a cross-sectional view similar to FIG; 6 butshowing a sealhaving alternate retention means.

Referring more specifically to the drawings, numeral 10 generallyindicates an internal combustion engine having a rocker cover 12 mountedon a cylinder head 14 to enclose a valve mechanism chamber 16. Cylinderhead 14 has integrally 52 by portion of the retainer.

A poppet valve 24 controls the flow of fluid from passage 22 to theengine combustion chamber 26 and includes a stem 28 which isreciprocably disposed in bore 20 extending therethrough into cavity 16.The end of the valve stem is engaged by valve actuating mechanismcomprising rocker arm 30 and push rod 32 to reciprocably actuate thevalve in a contake passage 22.

As shown in FIG. 2, seal assembly 38 comprises a thin sheet of sealmaterial 40 retained and supported by a sheet metal retainer 42. Sealmaterial 40 preferably consists of a filled polytetrafluoroethylene(Teflon) material having high resistance to abrasive 'wear, one exampleof which is a homogeneous mixture containing 70 percent Teflon, 19percent glass and l 1 percent red lead oxide. The material is relativelythin having, for example, a thickness of approximately .0l5 inches andis formed with a frustoconical lip 44 having the smaller diameter end 46in contact with the valve stem 28. The larger diameter end 48 connectswith a radial flange portion 50 which sealingly engages the end surface52 of a counterbore 54 formed in the end 19 of the valve guide. At theouter edge of flange portion 50, a short lip 56 extends upwardly toengage the sides of the counterbore 54.

Sheet metal retainer 42 is preferably formed of a spring steel and issubstantially coextensive with seal material 40 having a frustoconicalportion 58, a radial flangeportion 60 and a short outer lip portion 62lying along portions44, 50 and 56 of the seal materialrespectively.Frustoconical portion 58 includes a plurality of -slots.64extending from its small end about two-thirds of the distance to thelarger end to form resilient fingers 66 which lie along the smaller endof lip 44 and urge the end 46 thereof into engagement with the valvestem. At the same time, lip 62 holds seal portion-56 into engagementwith the counterbore 54 to hold the seal assembly tightly in place inthe valve guide. The radial flange portion 50 of the seal material isheld in sealing engagement with surface Seal lip 44 and resilientfingers 66 are of substantial length to provide allowance for slighteccentricity of the counterbore or retainer lip with respect to thevalve guide bore.

Referring now to FIGS. 3 and 4, the construction 38a is identical .tothat of FIG. 2 with the exception that lips 56and 62 of thesealmaterialand retainer respectively are crimped to have alternatelyinwardlyand outwardly deformedportions 68 and 70 respectively 'tostiffen the lip andprovide for better retention in the counterbore. Itshould be apparent-that if desired the short lip portion-56-of theseal-material could be eliminated and lip 62 of'the retainermadeslightly larger toengage directly the counterbore 54.

Referring now to FIGS. 5 and 6, an alternate embodiment of the inventionis shown before and after installation. This emformed therein aplurality of valve guides 18, only one of which is shown in order tosimplify the drawings. Valve guide 18 terminates in a cylindricalprojectingportion l9 and includes an axial bore 20 which extendsbetweencavity 16 and an intake passage 22 of the cylinder head.

b'odirnent includes acsheet metal retainerj72" formed ;in a cuplikeshape having a generally flat'base .74 and a cylindrical sidewall 76.Sidewall 76 includes identations .18 fora; purpose to be subsequentlydescribed; The 'base includes asmallcen- -tral opening. 80 having aplurality of slotsi82 -radiating outwardly therefrom. The slots'82terminate about two thirds of the way to the edge in small openings 84';thus forming avplu- .rality of inwardly extending resilient fingers85.

' Disposed alongthe innersurface of the base'74 is athin disc 86 of sealmaterial formed from aawear resistant filled Teflon material. Disc 86hasxacentral openingv approximately equivalent'in :size to-opening-80and its-outer diameter is slightly largerthan the interior of. wall 76so' that the 'discis retainedin'placeupon installation.

The construction'shownin FIG; S isready to be installed .upon a valveguide '90 of the type shown in FlG. 6-which;is

identical to that shown in FIGS. 2 and 3 except for the absence of thecounterbore. The seal assembly is installed on the valve guide beforeinstallation of a valve in the guide and this is accomplished by forcingthe sidewall 76 over the outside of the guide so that it is gripped bythe identations 78 which then retain the assembly in place on the end ofhe valve guide.

When the assembly is in place, a forming tool (not shown) havingessentialy the diameter of valve stem 28 is thrust upwardly through thevalve guide forcing the inner portions of disc 86 upwardly. Due to theformability of the Teflon material, the disc portion is deformed by thisaction into a frustoconical lip 44 similar to that of FIG. 2. At thesame time fingers 85 are bent upwardly between the locations of openings84 to support portion 44 of the seal material and urge its smallerdiameter end 46 inwardly such that upon installation of the valve stem28 in the guide, the seal is held in engagement therewith as shown inFIG. 6.

The outer portion of disc 86 remains in place to form a radial flangeportion 50 and is retained in engagement with the end 92 of the valveguide by a mating radial flange portion 60 which is formed by theportion of base 74 outboard of openings 84.

The forming in place of the seal lip and bending of the spring fingersto their final positions in the manner described has the advantage thatthe seal opening is automatically aligned with the valve guide bore thusaccounting for greater eccentricity of the bore and the guide outerdiameter than would be the case with a seal assembly completely formedprior to assembly.

Referring to FIG. 7 a seal construction identical to that of FIG. 6 isshown except that indentations 78 are eliminated from the retainermember and are replaced by inwardly deformed barbs 94 which retain theseal assembly in place by gripping the outer surface of the valve guide.

lclaim:

l. A VALVE STEM SEAL ASSEMBLY FOR USE IN AN INTERNAL COMBUSTION ENGINEHAVING A VALVE GUIDE WITH A LONGITUDINAL BORE AND A POPPET VALVE WITH ASTEM RECIPROCABLY RECEIVED IN SAID BORE, SAID SEAL ASSEMBLY COMPRISING:

a thin sheet of wear resistant filled Teflon material, said materialhaving a relatively long generally frustoconical lip with a mallerdiameter end adapted to sealingly engage the valve stem and a largerdiameter and connecting with a radial flange portion adapted tosealingly engage the valve guide;

a sheet metal retainer having a plurality of resilient fingers lyingalong and supporting the outer surface of said lip and terminating closeby said smaller diameter end, said fingers urging said smaller diameterend inwardly to engage the valve stem, a radial flange supporting saidresilient fingers and lying along the radial flange portion of saidmaterial to hold said radial flange portion in contact with said valveguide and means connecting with said retainer radial flange to securethe seal assembly to the valve guide;

said sheet metal retainer including a frustoconical portion havingsmaller and larger diameter ends, said resilient fingers forming a partof said portion and being separated by a plurality of slots extendingfrom said smaller diameter end at least part way to the larger diameterend; 7

'said means to secure the seal assembly to the valve guide comprising ashortlip extending longitudinally from the outer edge of said flangegenerally in the direction of said fingers, said valve guide having acounterbore at the end of said bore and said short lip being sized tofit tightly into said counterbore to retain said seal assembly in placeon said valve guide; and

said short lip being scalloped with alternate inwardly and outwardlydeformed portions around its perimeter so as to stiffen said short lipand limit its contact with said counterbore to said outwardly deformedportions.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 554 562 Dated January 1 2 1 971 Carl 1' sl 0 R Dav i s Jr Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2 line 7 beginning with "A COIL SPRING" cancel to and including"DIRECTION" in line 10, same column 2, and insert A coil spring 34extends between the cylinder head and a valve carried seat member 36 tobias the valve in a closing direction Column 3, line 36, beginning with"VAI and including "COMPRISING" in line 3 of column 4, should app inlower case letters Column 4 line 9 after the semicolon,

insert and Signed and sealed this 16th day of May 1972 (SEAL) Attest:

EDWARD M. FLETCIIER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patent

1. A VALVE STEM SEAL ASSEMBLY FOR USE IN AN INTERNAL COMBUSTION ENGINEHAVING A VALVE GUIDE WITH A LONGITUDINAL BORE AND A POPPET VALVE WITH ASTEM RECIPROCABLY RECEIVED IN SAID BORE, SAID SEAL ASSEMBLY COMPRISING:a thin sheet of wear resistant filled Teflon material, said materialhaving a relatively long generally frustoconical lip with a mallerdiameter end adapted to sealingly engage the valve stem and a largerdiameter and connecting with a Radial flange portion adapted tosealingly engage the valve guide; a sheet metal retainer having aplurality of resilient fingers lying along and supporting the outersurface of said lip and terminating close by said smaller diameter end,said fingers urging said smaller diameter end inwardly to engage thevalve stem, a radial flange supporting said resilient fingers and lyingalong the radial flange portion of said material to hold said radialflange portion in contact with said valve guide and means connectingwith said retainer radial flange to secure the seal assembly to thevalve guide; said sheet metal retainer including a frustoconical portionhaving smaller and larger diameter ends, said resilient fingers forminga part of said portion and being separated by a plurality of slotsextending from said smaller diameter end at least part way to the largerdiameter end; said means to secure the seal assembly to the valve guidecomprising a short lip extending longitudinally from the outer edge ofsaid flange generally in the direction of said fingers, said valve guidehaving a counterbore at the end of said bore and said short lip beingsized to fit tightly into said counterbore to retain said seal assemblyin place on said valve guide; and said short lip being scalloped withalternate inwardly and outwardly deformed portions around its perimeterso as to stiffen said short lip and limit its contact with saidcounterbore to said outwardly deformed portions.